Along with the demand for LTE-A, more and more attention is paid on the cell average frequency spectrum efficiency and the cell edge frequency spectrum efficiency. By comparison, more attention is paid on the cell edge frequency spectrum efficiency, mainly because the uplink and downlink of the LTE-A system are frequency division systems which take orthogonal frequency division multiplexing (OFDM) as basic multiple access multiplexing. The difference between the frequency division system and the traditional wireless communication system which takes code division multiple access (CDMA) as the basic multiple access multiplexing is that, the LTE-A system has no processing gain and there is almost no interference problem within the cell because of the full orthogonal frequency-division, but interference processing at the cell edge is relatively difficult.
In order to effectively solve the problem of the interference processing at the cell edge, CoMP technology is introduced. The CoMP technology is: transmitting in coordination by using transmitting antennas of multi-cell to achieve relatively high capacity and reliable transmission of wireless links at the cell edge. FIG. 1 illustrates a basic schematic diagram of a CoMP, comprising: a base station 21, a base station 22 and a base station 23; a cell 11 in which the base station 21 is located, a cell 12 in which the base station 22 is located, and a cell 13 in which the base station 23 is located; a user equipment (UE) 31, a UE 32 and a UE33. In FIG. 1, the cell 11, the cell 12 and the cell 13 provide services in coordination for the UE 32 by using the CoMP technology.
In order to clarify the related concepts of the CoMP, the related concepts of a CoMP domain and a CoMP active set are defined on the 56th 3GPP meeting. Cell entity for measuring and/or reporting by the UE (CoMP Reporting Cell Set, CRCS) includes three aspects of content as follows: first, the CRCS is centrally determined by the network and notified by the serving cell to the UE; second, the case that the UE can coordinate the determination of the CRCS is not excluded; and third, the CRCS is semi-statically configured. Among them, the CoMP active transmission point set (CATS) practically serving the users also contains three aspects of content as follows: first, the CATS is determined by the network, and it might be different for different UEs; second, the UE can know or not know the CATS; and third, the CATS is dynamically configured or semi-statically configured.
In the CoMP research path formed in the 3GPP 55bis meeting, the corresponding channel quality is only the channel quality between the UE and the primary serving cell when demodulating the control information carried in a control channel on the UE, due to it is pointed that interaction is performed only between the UE and a single cell, i.e., the primary serving cell, for the above-mentioned control channel, such as physical downlink control channel (PDCCH), physical control format indicator channel (PCFICH), physical hybrid ARQ indicator channel (PHICH), physical broadcast channel (PBCH), or primary/secondary synchronization channel (P/SCH); however, for a traffic channel, such as physical downlink share channel (PDSCH), paging channel (PCH), or dedicated broadcast channel (DBCH), the corresponding channel quality is a comprehensive channel quality formed by all cells in the CATS when demodulating the traffic data bore in the above-mentioned traffic channel. Therefore, in CoMP feedback, it needs to consider the difference between the CQI feedback in the control channel and the CQI feedback in the traffic channel.
FIG. 2 illustrates a schematic diagram of transmission nodes of control information and traffic data in CoMP multi-point joint transmission, comprising: a UE1; a base station 1, a base station 2, and a base station 3; cell 1 in which the base station 1 is located, cell 2 in which the base station 2 is located, and cell 3 in which the base station 3 is located; pilot 1 transmitted by the base station 1, pilot 2 transmitted by the base station 2, and pilot 3 transmitted by the base station 3; a first weight w1, a second weight w2, and a third weight w3. In CoMP multi-point joint transmission, control information 1 of the UE1 is sent from the primary serving cell, i.e., the cell 1, to the UE1, that is, interaction is performed only between the primary serving cell and the UE for the control channel. A formula of the corresponding received signal is: Yc=H1Sc+N1; wherein, Sc denotes the control information of the control channel, H1 denotes the channel quality between the cell 1 and the UE1, and N1 denotes the received noise and interference. Traffic data, i.e., the traffic data 1, traffic data 2 and traffic data 3, in the same sub-frame are sent by all cells, i.e., cell 1, cell 2 and cell 3, in the CATS to the UE1, that is, for the traffic channel interaction is performed between the UE and all cells including the primary serving cell. A formula of the corresponding received signal can be: Yd=(H1W1+H2W2+H3W3)Sd+N; wherein, Sd denotes the traffic data of the traffic channel, H1 still denotes the channel quality between the cell 1 and the UE1, H2 denotes the channel quality between the cell 2 and the UE1, H3 denotes the channel quality between the cell 3 and the UE1, and N denotes the received comprehensive noise and interference.
In summary, on the one hand, from the perspective of channel characteristic, the corresponding channel characteristic of the control channel is H1, and the corresponding channel characteristic of the traffic channel is the comprehensive channel (H1W1+H2W2+H3W3) formed by all cells in the CATS. On the other hand, from the perspective of interference signal, for the control channel, since the control channel only interact with the primary serving cell, and the same resource in the adjacent cell might also transmit other control information besides of the control information interacting with the primary serving cell, there is interference to the control information transmitted between the primary serving cell and the control channel; and for the traffic channel, the same resource transmits the same data, it can be seen from the above that the interference signal in the control channel is stronger than that in the traffic channel.
Combining of the above-mentioned factors, it will lead to a greater difference between the channel quality of the control channel and the channel quality of the traffic channel. However, CQI feedback in the prior art only relates to one cell to provide services for the UE, due to it does not involve the introduced CoMP technology, thus there is no problem on the difference of the CQI feedback. In other words, for the CQI feedback with the introduced CoMP technology, there is not a solution on the CQI feedback yet, let alone a solution to avoid the difference of the CQI feedback after introducing the CoMP technology.